1. Field of the Invention
The present invention relates to an ink-jet recording apparatus which jets inks of a plurality of colors.
2. Description of the Related Art
There has conventionally been known an ink-jet recording apparatus which performs recording to a recording medium by jetting inks of a plurality of colors from a recording head. An ink-jet recording apparatus described in U.S. Patent Application Publication No. US 2005/151796 A1 (corresponding to Japanese Patent Application Laid-open No. 2005-193579) includes two recording heads, and on each of the recording heads, a plurality of nozzle rows corresponding to inks of a plurality of colors (a plurality of color inks), respectively, are arranged in parallel, and in each of the nozzle rows, a plurality of nozzles are arranged in a line. These two recording heads are supported on a bottom of a head holder to face a recording medium. In each of the recording heads, a cavity plate formed of a stack of a plurality of plates, a piezoelectric actuator, and a flexible wiring member extending in a direction in which the nozzle rows are arranged are stacked. On the flexible wiring members, IC chips, as driving circuits for driving the piezoelectric actuators, are provided and are partly in contact with a heat sink in a heat conductive manner.
In recent years, in response to a demand for a higher speed and a miniaturization of an ink-jet recording apparatus, processing speed of a driving circuit, the number of nozzles of recording heads, and integration density have been made on an increasing tendency. With this tendency, an amount of heat generated by the driving circuit has become larger. Accordingly, the temperature of a heat sink itself for releasing the heat of the driving circuit has become higher, which then has led to an increase in temperature of the whole space in a head holder holding the heat sink. The heat of the driving circuit is also transferred or transmitted to ink tanks in the head holder and to the recording head, via the space in the head holder, thereby heating inks flowing through the inside of the head holder also. As viscosity of the ink becomes lower due to the increase in the temperature of the ink, the jetting velocity or speed of the ink becomes higher, which in turn causes deviation from an intended landing position, variation in dot diameter, and/or the like, resulting in unstable jetting accuracy. Furthermore, due to variation in heat influence among the inks, there occurred variation in temperature among the inks, which has been a cause of deterioration in printing quality.
Generally, an ink-jet recording apparatus uses not only inks of basic colors of yellow, magenta, cyan, and black but also inks of intermediate colors such as light yellow and light magenta and inks of red, green, and blue, thereby eliminating granular texture and realizing printing quality rich in color tones. If deviation from an intended landing position or variation in dot diameter occurs in these inks, a printing error of a deeper ink color is more emphasized or more conspicuous (visible) and a printing error of a lighter ink color is less conspicuous. Conversely speaking, a printing error such as deviation from the landing position or variation in dot diameter of some color is more conspicuous to human eyes and a printing error of some other colors is less conspicuous to human eyes. Here, the term “light-color ink” refers to an ink of low-visibility color such as, for example, a yellow ink, and the term “deep-color ink” refers to an ink of high-visibility color such as, for example, a black ink.